In metal connection in electrical and electronic devices or the like, solder connection using a solder paste has been generally used and in such a solder paste, a solder alloy containing lead has been conventionally used.
However, in view of environmental load, the use of lead has been recently required to be suppressed and thus, the development of a solder alloy without containing lead (lead-free solder alloy) has been promoted.
As such a lead-free solder alloy, for example, a tin-copper alloy, a tin-silver-copper alloy, a tin-silver-indium-bismuth alloy, a tin-bismuth alloy, and a tin-zinc alloy have been well known and among all, a tin-silver-copper alloy, a tin-silver-indium-bismuth alloy, and the like have been widely used.
As such a lead-free solder alloy, to be more specific, an Sn solder alloy containing Ag at a ratio of 0.5 to 5 weight %, In at a ratio of 0.5 to 20 weight %, Bi at a ratio of 0.1 to 3 weight %, furthermore, at least one kind selected from the group consisting of Sb, Zn, Ni, Ga, Ge, and Cu at a ratio of 3 weight % or less, and Sn as a remaining content has been proposed (ref: Patent Document 1).
In addition to the description above, as such a lead-free solder alloy, for example, a solder material containing Ag at a ratio of 1.0 to 4.0 weight %, In at a ratio of 4.0 to 6.0 weight %, Bi at a ratio of 0.1 to 1.0 weight %, furthermore, at least one or more elements selected from the group consisting of Cu, Ni, Co, Fe, and Sb at a ratio of 1 weight % or less, and Sn as a remaining content has been proposed (ref: Patent Document 2).